Did we make incredible leaps ahead when there was no ethical standards? Did Watson HAVE to traumatize a young infant to demonstrate behaviorist tenets? Simply put, no. The advancement rate has been much more impacted by technology.
If every question can be approached through ethical means, then the question of advancement becomes moot anyhow. They should reveal the same answers.
Of course, you seemed to have neglected "natural experiments" that are utilized in psychology all the time and allow us to conduct work that would otherwise be unethical. For example:
Does the sexual preference of your parents influence the sexual preference of children?
This question would be unethical, if not impossible, to conduct in an experimental fashion. We can not assign sexuality to a partcipant. However, this experiment is being conducted everyday in this nation. A new population of homosexual parents are emerging. All we have to do is wait in the wings and collect the data.
Other examples include patients with specific brain traumas. Read "Anthropologist on Mars" by Oliver Sax. These are "natural experiments" that do not require the lesioning of actually healthy human brains (i.e. yours or mine).
I do recognize that ethics are socially constructed. At some detailed level politics do influence the ethics of some (i.e. Terri Shiavo), however the ethical standards to which I refer are at a general level, and merely ask that no harm, physical or psychological be experienced by the participant and their information be kept confidential. This is standard IRB stuff...
If you want to swath this conversation in gray, I won't object. However, there is a reasonable level and appropriate standards in which it can be evaluated.